Carboxyl-Terminal Modulator Protein (CTMP), a Negative Regulator of PKB/Akt and v-Akt at the Plasma Membrane

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Science  12 Oct 2001:
Vol. 294, Issue 5541, pp. 374-380
DOI: 10.1126/science.1062030

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The PKB (protein kinase B, also called Akt) family of protein kinases plays a key role in insulin signaling, cellular survival, and transformation. PKB is activated by phosphorylation on residues threonine 308, by the protein kinase PDK1, and Serine 473, by a putative serine 473 kinase. Several protein binding partners for PKB have been identified. Here, we describe a protein partner for PKBα termed CTMP, or carboxyl-terminal modulator protein, that binds specifically to the carboxyl-terminal regulatory domain of PKBα at the plasma membrane. Binding of CTMP reduces the activity of PKBα by inhibiting phosphorylation on serine 473 and threonine 308. Moreover, CTMP expression reverts the phenotype of v-Akt–transformed cells examined under a number of criteria including cell morphology, growth rate, and in vivo tumorigenesis. These findings identify CTMP as a negative regulatory component of the pathway controlling PKB activity.

  • * Present address: Center for Research in Occupational and Environmental Toxicology, Oregon Health Science University, Portland, OR 97201–3098, USA.

  • Present address: Department of Biochemistry, Royal Perth Hospital, GPO Box X2213, Western Australia 6001, Australia.

  • To whom correspondence should be addressed. E-mail: hemmings{at}

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